Inhibition of gelation in unsaturated polyesters with salts of amines



Patented July 21, 1953 INHIBITION OF GELATION 1N UNsA'rur RATED POLYESTERS WI'ru-sA s or AMINES Earl v P enMi Wa wisaassi ne t P ts.-

burgh Plat eGIass Company; All Pin, a corporation'of Pennsyvan a N0 Drawing. Application O tob .1959, S ria 191$! 1 The present invention relates to stabilizatiqn of polymerizable esters of dihydric or other polyhydric alcohol esters of polycarboxylic acids which contain a polymerizable ethylenically unsaturated group, preferably in the alpha beta position and to stable compositions comprising such esters. 1 I

One object of the invention is to provide a polymerizable material of the foregoing type which is stabilized against premature 'gelation during relatively prolonged periods of storage.

A second object is toprovide' a material which is stable during extended periods of-storage'but which can readily be cured to a resinous state under-appropriate conditions.

A third object is to provide a stabilized oom-v 7 position of the foregoing type which is highly.

resistant to gelation in the absence of peroxide catalysts of polymerization but which resinifies quickly at relatively low-temperatures when a catalyst is added.

A fourth object is to provide such copolymer- .izable mixtures which will cure readily to provide relatively large castings which are sound and of good color.

These and other objects will be apparent from consideration .of the following specification and the appended claims.

i9 Qiai ns. (01. 2s0 45.4)

2 istry, December 1939, page 1512 and January 1940,,page 6 4.

' The foregoing .polymerizable compositions undergo addition reactiomYthat is reaction at the points ,of" carbon-carbon un aturation, eve'niin the h e mv ,H po mer zat ca j lys fland a room temperature or thereabouts'. This is' especially true in the .case'l'of .copolymerizable mixtures of the polyesters and thejethylenically, or vinylically unsaturateid' inono'rners. A polyester of maleicor fumaric'ac d'la glycol such as propylene glycol or "d hylne' glycol, in the presence of a vinyl ic monomr such as styrene, unless inhibited, will begin tdgel almost at once. This is true evenfi n 'th absence of polymerization catalysts "and at omftemperature. A catalyst may be desirable-to obtain complete cure of such mixture in a" reasonable time, but nonetheless, polymerization'will' quickly proceed so far in the uncatalyzed mixtures as to prevent or atleastinterfei e'with normal casting or lamina'ting' operations.

-- t' has he'retofore been recognized that linear polyesters 0f dihydric alcohol sand an ethylen; icall y unsaturated dicarboxylic acid in which the .carboxylic groups are linked to o'ne or both of the Jethylenic "carbon atoms, (inliu'iing rn'ixe' cl esters "of such ethylenically unsaturated .dicarboxylic acids and othendi'carboxylic acids) are capable of polymerization by addition reaction between the ethylenic groups of the polyester to form thermoset products.' This 'type of material is widely disclosed, forQeXamblein U. S. Letters Patent Nos. 2,409,633 and 2,443,735 to 2,443,741-inclusive, grantedito Kropa or U. S. Letters Patent 2,450,552 granted 'to'I-Iurdis.

It has also been suggested to admix liquid, or at le t fusible linear polyesters such as are disclosed in the .foregoing patents, with ethylenically unsaturated monomers and copolymerize IHQ Qn f f p s mples of libliqatiens ar 9 9? ii mesa-a nd En n e in course, greatly ,r

This strong tendency of .the copolymerizable mixtures to' set' 'jprematiirely was early recognized ,(se Ellis,Patent{2,-255,313 In the patent, it is proposed to improve this property by injcorporating a. cellulose as a "filler. This, of

h f str'icts the field of application .of'them'ixtures."

' It has" further beenproposed to improve the storage characteristics of the copolymerizable mixtures by adding small amounts of stabilizers such as phenolic compounds, e. g. hydroquinone. U. S. Patent 2,409,633 contains such suggestion. However, for many applications, the phenolic compounds were"'pobr"' inhibitors of 'gelation. They often continued to inhibit the polymerization even 'wheifthe 'catalystwas added and the mixturecwas heated. Therefore, they .unduly slowed up the v.. .ct n.anc -.n ted un uly high curing temperatures. :This was objectionable in making castings. Some inhibitors also tended to discolor the'resins, a feature highly objectionable in the ,casting art. Castings of substantial size also t rid d strongly to crack or break in the curing o at s.

According to the pre nvention, a novel stable resinifiable' os on" which is highly stable in storage, bu' rch will cure readily without substantial dis oloraition 'of cracking, has

1y unsaturated dicarboxylic acid stabilized by a soluble amine salt which when dissolved in water forms a solution of. a pH of substantially '7 or below in which such salts may be regarded as derivatives of ammonium salts in which 1 to 3 hydrogen atoms directly attached to the ammonium nitrogen are replaced by an organic radical or radicals. In accordance with this invention it has been found that such amine saltsare excellent gelation inhibitors or stabilizers for polyesters of the foregoing type or for mixtures of such polyesters and vinylic monomers. These salts are of the type resulting from reaction of a primary, secondary or tertiary amine with an acid.

The polymerizable mixtures The polymerizable mixtures to be stabilized The ethyiem'cally unsaturated dicarbomylic acid It is apparent that an appropriate ethylenic unsaturated dibasic acid for use in thepreparation of an ethylenically unsaturated polyester may comprise a large class. Some of them, designated as component A, are tabulated as follows:

TABLE A Maleic acid Fumaric acid Aconitic acid Mesaconic acid Citraconic acid Ethyl maleic acid Pyrocinchoninic acid Xeronic acid taconic acid Carbic acid The chlorine substituted derivatives of the acids,

e. g. chloromaleic acid, are also contemplated.

The anhydrides of these acids, where the anhydrides exist, are, of course, embraced under the 4 Halogen substituted glycols, e. g. mono-chlor derivatives are contemplated.

The saturated dicarboxylic acids It is to be understood that in addition to stabilization of unmixed esters the invention contemplates the stabilization of mixed polyesters of dicarboxylic acids in which the polyester molecule is of both an ethylenically unsaturated dicarboxylic acid and a dicarboxylic acid free of any unsaturation adapted to react by addition with ethylenic groups. The principal functioning groups in these non-ethylenic acids are carboxyls that react by esterification. Such acids in the polyester add to the length of the polyester m0lecules but they do not cross link the polyester molecules at points intermediate their ends by addition with the monomer. Often such nonethylenic dicarboxylic acids improve the properties of the'resins in which they are introduced. In most instances the mixed polyesters are pre- I ferred.

term acid, since the reaction products or polyesters are the same. Often it is preferabl to operate with the anhydride rather than the free acid. All of these acids are dior tricarboxylic. Most of them include an ethylenic group in a relation to at least one carboxyl. That is, they include the group The acids (or anhydrides) which are a B ethylenic a {3 dicarboxylic are especially desirable.

The dihydric alcohols The dihydric alcohols termed component (B) of the polyester embrace such compounds as are included in the following table:

TABLE B Examples of appropriate dicarboxylic or tricarboxylic acids of the second class are tabulated as follows:

TABLE C Phthalic acid Tetrachlorophthalic acid Succinic acid Adipic acid Suberic acid Azelaic acid Sebacic acid Dimethyl succinic acid Chlorinated derivatives of the above acids, 1,

3-8 inclusive For purposes of the present invention, the aromatic nuclei of such acids as phthalic are regarded as saturated since the double bonds do not react by addition as do ethylenic groups. The term acid also contemplates the anhydrides of the acids. Mixtures of any two of the acid 1 to 9 are contemplated.

Naturally some of the members of Tables A, B and C are preferable to others. For example, some of them may presently be unduly expensive, but since this condition is often subject to change, they are properly to be included.

Monobasic acid component It may also be desirable to include a small amount of a drying oil acid or other monocarboxylic acid in the polyester. Drying oil acids impart air drying characteristics to the polyester, or the mixture of the polyester and the vinylic monomer. Appropriate acids termed acid D include those of the following table:

TABLE D Linolenic acid Linoleic acid Elaeostearic acid Octadecatrienoic acid Clupanodonic acid Acetic or propionic acid es ew Mixtures of these acids are contemplated; In addition to or in lieu of the above, monohydric alcohols including ethyl, propyl, allyl or like alcohol may be incorporated in the polyester.

Preparation of the polyester In the preparation of the polyesters, the dihydric alcohols of Table B which preferably contain no more than 10 carbon atoms are usually attests slightly in excess of such equivalency' of the sum of the acids of Tables A, C and fii 'Tls'ually, this excess will not much exceed-i or and'it may be lower. The excess glycol facilitates reduction "of the acid number of the polyester.

The ethylenically unsaturated dicarboiiylic acid may constitute the whole of the acid component of the polyester, butusually it is preferred to include at least some of one or more of the non-ethylenic acids from Table C. The amount of acid or acids from the latter table is capable of variation over abroad range. The minimum is, of course, none. at all, and the maximum may be 10 or 12 mols per mol ofthe acid from Table A. Naturally, as the percentage of the acid from Table C is reduced, the polyester assumes more and more closely the character of the polyester containing only acid or acids irom Table A. It is impossible to state an absolute minimum to theeffective amount of acid from Table C.

Amounts at least as low-as /5 mol permol of the first menti'on'edacids are suggested.

- A component from Table Dis also optional,

dependent upon whether an air drying poly' ester is desired. A range of one mol of acid-D to 2 to 12 mols of acids A or A' and C is suggested.

Appropriate ranges of the several components of the polyester may be tabulated. as follows:

,Component: 7

, (A) Ethylenic'dicarboiiylic acid; its 12 inch.

(or Non-ethylen'ically unsaturated dicarboxylic optional, but if present, 75 to vi i ,mols. r

(D) Drying oil acid ptioiiaiput if present,

1 mol per 2 to 1'2 mois A+o. h (B) Dihydric alcohol, equivalent or in slight excess of A+C+D. Conditions ofereactionin preparing polyester In conducting the esterification of the dihydric alcohol and the acid or acids, conventional principles are adhered to. Add catalysts may be added. The reaction may beconductedunder an atmosphere of carbon dioxide or nitrogen as.

Xylene or other non-reactive solvent may be included and the reaction may be conducted by heating the mixture to reactioii temperature, e. g. to that at which water is expelled from the system. It is continued until water ceases to evolve and the acid value of a sample reasonably low, e. g. 5 to 50. It should not be continued so long as to result in infusibility of the polyester. Usually a temperature of 150 to 190'or 200 C.

and a reaction time of 2th 20 hours is suificient to effect the esterificatioii.

Stabilizing the polyester composition It is usually desirable to add the ammonium type amine salt to the-polyester in the absence of monomer. If monomer is to be added it can be incorporated with the. previously stabilized polyester. 'To this end, the amine salt is conveniently added to the polyester while it-is warm.

tertiary amines which are either neutral or have an acid reaction. Such salts include the chlo- 'by the general formula:'

amine rides, brcriiides, iodides, siiifates and classmat s as well as the carbcxyiic acid salts such as formic acid salts, acetic acid salts, propionic acid salts, butyric acid salts, succinic acid salts, maleic acid salts and salts of other acids capable of reacting with the primary, secondary or tertiary amine molecule to form salts and where the nitrogen of the amine becomes pentavalent. It desirable that the salt be reasonably soluble in the mixture to be stabilized. Preferably strongly oxidizing" acids, such as 'nit-ric acid, are excluded. The tertiary amine salts usually are embraced R1 X Ri=N-H I, where X is the acid-radical of an acid at least as strong as acetic acid and having the oxidizing power notgr'eater than that of sulphuric acid, and where R1, R12 and Rs are the radicals of the l tat, it Most advantageously the group R1 is a hydrocarbon group containing to 13 carbon atoms and being alk'yl in a normal or branched chain, e. ethyl, methyl, propyl, butyl, ain'y'l, hexyl or cetyl or aryl or aralkyl, e'. g. phenyl, benzyi, alpha naphthyl or b'eta naphthyl; etc. The invent-ion also includes the use of salts of substituted amines in which the radical Riis a substituted hydrocarbon radical 7 containing one or more chlorine, bromine, iodine, acyl, carbonyl or the like substituents in the chain. R2 and Rimay be from the same family as R1 or one or both may be hydrogen. Groups R1 or R2 may be joined to each other in a ring structure, for example as represented by the formula: 1R1 x Ii N- -H where X is the acid radical or group. R2 and Rs may be combined in a common ring-like radical or a chain (CHzht where n is a whole number, e. g. 4dr 5. R1 canbe a separate radical or the 'N atom can be doubly bonded to R3.

While the structures of the compciiiids correspond to that resulting from reaction of a primary or secondary or tertiary amine with an acid to form an ammonium salt, the mode of forming these salts is not a part of the invention.

The invention contemplates the use of the salts as stabilizers in the polymerizable' materials herein disclosed, regardless of the techniques employed in preparing the salts. Often the reaction may not involve the interaction of acids and amines. For example, an alkyl halide may be reacted with ammonia to form a salt. Such reaction might be represented by the equation:

RC1+NH3 RNTI3CI Where R is alkyl, e. g. ethyl or methyl.

In the formulae the organic groups R1, R2 and R3 may be of a single kind or they may be mixed. All of them may be hydrocarbon such as alkyl, alkenyl or alk'ynyl, e. g; ethyl, methyl, propyl, isopropyl, n-butyl, secondary butyl, tertiary butyl, vinyl and methallyl. A part may be aryl or aralkyl, e. g. phenyl, benzyl, etc. Moreover, groups R1, R2, and R3 may be oleyl, stearyl, methoxy or methoxy benzyl smears Some of the possibilities for the several groups R1, R2 and R3 are tabulated as follows:

TABLE E Benzyl yl chlorobenzylnh Chlorobenzyl.

Cetyl Get Octadecyl Octadecyl. Chlr0methl Chloromethyl.

Methoxymethyl. Methoxymethyh Methoxymethyl.

It is to be understood that the various possible combinations of the groups 1 through 17 in the several positions R1, R2 and R3 are contemplated. That is, the compounds may be homogeneous or so mixed as to include any combination of the above groups desired.

As stated previously, halogenated alkyl, aryl or aralkyl groups are contemplated. For example, the hydrocarbons of 1 through 14 may tcontain l, 2 or more chlorine or bromine atoms.

In some instances, as previously indicated, it will be apparent that two or" the groups R are joined or interconnected in a ring structure. This is represented by the piperidinium salts. Salts of the formula:

where n is a whole number, e. g. 2 or 3, and R1 and X are as above defined, and also belong in a The acid component of the salt As previously stated, the acid component of the salt of the amine may be selected from a relatively wide range of acids. For example, the radical X may be Cl, Br, I,

These latter twosalts may be acid orneutral salts. The acid may also be organic as previously indicated, that is, the radical of the acid will be of the approximate formula:

where R is a hydrocarbon group such as alkyl or the remainder of the molecule in a dicarboxylic acid such as succinic, maleic or fumaric acid. Of course, R may also be a halogen substituted hydrocarbon such as trichloromethyl, mono-, dichloroor bromoethyl, propyl or the like. The

. inhibitors, as indicated, can be regarded as salts of acids and amines.

The following table is of examples of acids which may be appropriately reacted with amines such as primary, secondary or tertiary amines to provide ammonium salts within the purview of the present invention:

TABLE F Acetic Succinic Sulfuric Phosphoric Hydrochloric Hydrobromic Chloroacetic Malonic Hydriodic 10. Maleic acid 11. Trichloro acetic In the acid component of the salt, Whose negative radical is represented by the group X, the latter group should be at least as strongly negative as acetic acid, i. e. should have a dissociation constant of at least l.'75 10- and should not involve heavy radicals or groups that would reduce its negative character or unduly impair its mobility in the mixture. The use of excessively heavy organic acidsto form the salts may also unduly increase the amount of salt required to attain stability. Organic acids employed preferably are of a weight not much above 200. The salts of the strong non-oxidizing mineral acids usually are the most satisfactory. The acid organic substitution products such as the acid sulfates, sulfonates and phosphonates of these acids are also contemplated.

The amino component of the ammonium salt The following constitute representative examples of amines which can be reacted with acids such as any of those selected from Table F to provide soluble ammonium salts adapted for use as inhibitors of gelation under the provisions of the present invention:

TABLE G Diethyl aniline .',Dimethy1 aniline Trimethyl amine Triethyl amine Tripropyl amine Tributyl amine Triamyl amine Trihexyl amine Diethyl amine Dipropyl amine Dibutyl amine Diamyl amine Dibenzyl amine Tribenzyl amine Pyridine a. N aphthyl amine N,N'Dicyclohexyl piperazine Piperidine The following are representative examples of salts of the amine which may b employed:

TABLE H Trimethylamine hydrochloride Trimethylamine hydrobromide Trimethylamine hydroiodide Dimethylaniline hydrochloride Dimethylaniline hydrobromide Triethylamine hydrochloride 7 Tri-n-butylamine hydrochloride 8. Tribenzylamine hydrochloride 9. Tribenzylamine hydrobromide 10. N Benzylaniline hydrochloride l1. Benzyl methylamine hydrochloride It is desirable that these salts be soluble in or compatible with thev polyester or mixture of polyester and monomer to be stabilized.

Dissolmng ammonium salts in polyester Salts of amines can be dissolved in polyesters of ethylenic dicarboxylic acids and dihydric alcohols (or their derivatives as modified by dicarboxylic. acids and/or drying oil acids) to provide products that can be stored for very long periods without fear of gelation. The stabilizers are preferably added to the polyester while. the latter is hot, e. g. 100 or 150 Ci A curing catalyst, e. g. benzoyl peroxide, tertiary butyl hydroperoxide, cyclohexyl hydroperoxide, aeetyl peroxide, lauroyl peroxide, or the like can be added to the stabilized mixture in appropriate amount (.01 to by weight) at any time. The mixture when heated will cure rapidly and completely with but little interference from' the inhibitor.

Copolymerizuble mixtures of polyesters and ethylenically unsaturated polymerizable compounds The copolymerizable mixtures of the polyesters and 'ethylenically unsaturated polymerizable compounds are, of course, frequently more reactive than the polyesters per se, and the stabilization of these mixtures is usually more urgent than that of the polyester. Such copolymerizable mixture may comprise any of the polyesters which, have alreadybeen'described and these may be incorporated with a suitable vinylically unsaturated monomer such as those referred to. in the foregoing patents.

V The ethylemc compounds The ethylenic compounds comprise any of the common ethylenic compounds capable of copolymerizing with the unsaturated'polyester. Preferably such compounds are liquids and usually they contain the reactive group H2C=C linked to a polar group. Generally they are used in the monomeric or syrupy polymer state. The following include some of these compounds:

TABLE I Styrene a Methyl styrene p-Methyl styrene Divinyl benzene Indene Unsaturated esters such as: 6. Vinyl acetate '7. Methyl meth-acrylate 8 9 1.7. Esters of3: monohydric unsaturated alcohols 10 (allyl, vinyl, methallyl, crotyl) and mono or polycarboxylic acids (acetic, propionic, succinic, etc.)

18. Esters'of 0.}3 unsaturated dicarboxylic acids (maleic, fumaric, itaconic) and monohydric alcohols (methyl, ethyl, propyl, isopropyl, amyl) Any one of these vinylic monomers (including syrupy mixtures of monomer and polymer) may be combined with any of the polyesters prepared from components A and B, A, B and C, A, B and D or A, B, C and D as previously described.

Mixtures of any two or more of the foregoing vinylic compounds and the polyesters are contemplated.

The vinylic monomer usually ,will comprise from 10 to 60% upon a Weight basis of the copoly-. merizable mixture and mixtures containing 20 to 40 or by weight of monomer are to be preferred. 1 a

v To formulate stabilized or non-gelling mixtures of (I) an unsaturated polyester of a dihydric alcohol and an acid comprising a dicarboxylic ethylenically unsaturated acid and (II) a vinylic monomer, it is preferred to dissolve a salt of an amine (for example one of those listed in Table H) as an inhibitor in the polyester component. This is best accomplished by adding the salt to the polyester while the latter is hot, e. g. about from Table I.- may beadded in appropriate amount, e. g. 10 to %-by weight of the monomer-stabilized polyester mixture, and at C. or lower temperatures.

The abovev method is particularly valuable when styreneisiused as the vinylic monomer since the mixture tends to polymerize upon formation unless stabilized. With less active vinylic monomers. theinhibitor may be added to the monomerflbefore' mixing if desired. The retional. amo'untsje. g. .1 to 5%, can be easily incorporated therein and the mixture may be readily cured. The temperature of cure can be moderate, .e. g.v below 100 C., but may be much lower, e. g. room temperature (22 C.) or thereabouts. Theresins may be further hardened-by baking, them. at to C. or thereabouts.

Higher temperaturesof initial curing and baking are. permissible. However, they should not be so; high as. to volatilizethe monomer (in initial cure) or to char .or discolor the final product.

Thetiine of. curing andbaking, of course, will vary greatly'depen'ding upon such factors as the size and thickne'ssof. the body to be formed and the temperature of reaction. Usually 5 minutes to-, 2. hoursis;sufficient. However, it is easy to This can be deterdetermine oy hardness tests when the articles are cured to hard, clear state.

It is an important feature of the use of the ammonium salts of amines herein disclosed as inhibitors of gelation, that although they are very efiective in periods of storage of the uncatalyzed mixture, the catalyzed mixtures cure very readily and completely at low temperatures and initiation of polymerization by peroxide catalysts is not seriously impeded by these inhibitors. Where the mixture is employed to embed delicate objects such as insects, biological specimens or the like, cure can be effected without damaging them. Also, in making castings in molds of latex or the like, the low curing temperature is desirable to avoid damage to the molds and production of fractured or impaired castmgs.

Thus, it is also a property of the salts that they do not discolor the product in which they are employed. Furthermore, castings formed from copolymerizable mixtures are sound and free of cracks. Products in which conventional inhibitors are employed during storage often are cracked or broken. This is especially true in the case of relatively massive castings.

It is to be understood that while the ammoni m or amine salts herein disclosed. taken by themselves, are excellent gelation inhibitors for conolymerizable mixtures of unsaturated polyesters and vinylic monomers, other inhibitors, such as those of conventional type, such as ouinone. can also be included along with the salts. These may be employed, for example. in a proportion of approximately 1% by weight based u on the weight of the salt or such other pro ortion as is expedient. Such additional inhibitors sometimes are helpful where the time and temperature of the cure is relatively unimportant and where it is desirable to increase the so-called tank li e of the mixture, that is, to increase the period in which catalyzed mixtures can be stored without gelation.

It is understood that such vinylie monomers as styrene, as sold commercially, normally contain small amounts of inhibitors to admit of stora e and shipment thereof without gelation or polymerization. Commercial monomers containing such inhibitors, e. g. quinone or hydroquinone, in small amounts can be employed in the present process. Obviously, the inhibitor in the monomer is greatly diluted when the latter is incorporated with a polyester under the provisions of the present invention. Also, in many instances, the effectiveness of the added inhibitor carried in the monomer has been greatly reduced by the period of storage which the monomerhas undergone before it is admixed with the polyester. Normally the inhibiting effect of the stabilizer in the monomer will not be objectionably great. However, if so desired, the inhibitor of commercial styrene or other monomer can be eliminated before the monomer is incorporated with a olyester containing an ammonium salt as an inhibitor.

While the use of the salts of primary and secondary amines is not precluded from the purview of the invention, it is usually preferred to employ the salts of the tertiary amines, such as trimethyl amine hydrochloride or dimethyl aniline hydrochloride orsimilar salts of tertiary amines. These salts, of course, should be soluble in the composition in the concentrations used.

The components of the stabilized copolymerizable mixtures of monomer and unsaturated poly- 12 ester preferably will be within the following proportions:

Parts by weight Vinylic monomer 10 to 60 Unsaturated polyester 40 to Salt of amine -z .01 to 2 The following examples are illustrative:

Example I "The results of these tests are tabulated as follows, percentages in the table being based upon the weight of the polyesterstyrene mixture.

Amount, Minimum Inhibitor Percent by Days, stawt. bility Triamyl amine hydrochloride .5 4 Pyridine hydrochloride 1.0 12 Alpha naphthyl amine hydrochloride 1.0 27 Diethyl amine hydrochloride l 1.0 2l

This constitutes a severe test; at like temperatures, the mixtures without inhibitors gel upon mixing.

Example II Diethylene fumarate adipate which was a polyester of equal mols of fumaric acid and adipic acid with diethylene glycol in approximately stoichiometric proportion to react with these acids was prepared and a stabilized mixture thereof with a monomer was formulated as follows:

Parts by weight Diethylene fumarate adipate 2 Diethylene glycol bis(allyl carbonate) 1 Trimethyl amine hydrochloride 0.015

This mixture was stable formore than 50 days at F. The control comprising a similar mixture except for the omission of the gelation inhibitor gelled in one day at a like temperature.

Example III Propylene adipate fumarate which comprised a mixed polyester of propylene glycol and equal mols of adipic acid and fumaric acid was prepared. This polyester can be stabilized with trimethyl amine hydrochloride in small stabilizing amount to provide a very stable polyester product. A copolymerizable mixture of good stability was prepared from the polyester by formulation as follows:

Parts by weight Propylene adipate fumarate 2 Diallyl phthalate 1 Trimethyl amine hydrochloride 0.015

This mixture was stable for more than 50 days at 150 F. The mixture without the stabilizer or inhibitor gelled in less than one day.

Example IV In this example, propylene adipate fumarate prepared in accordance with Example III was stabilized with trimethyl amine hydrochloride. The mixture was a good and stable polyester 13 which can be cured to form a resinous product by the addition. of an appropriate peroxide catalyst and subsequent heating to reaction temperature. A copolymerizable. mixture of the fo'11 v.ving

composition was. prepared from the stabilized polyester:

Parts. by weight Propylene fumarate adipate l 2, Vinyl acetate l. 1 'I'riinethyl amine hydrochlorid u..-- 0.0.1

The. resultant copol meriz ble ixture a Stabler more than 50 days at 150 and for 18.0 days at F. The. tebilizedmixtu e coul e atalyzed w th benz yl, r xide. or other pe x d t. List, for example amount 91.01. to 5% by eight. The. cataly ed mixture. would el at .2

o 50 C. andwouid cureread l hen heat d. for

example. t atemperatureei '75to' 200 C-v Eramnl V V A. p opylene adipate iumarate polyester re- "p ed as p evi usly d scri d w s st bil d,

or fumaric acid and a glycol such as propylene glycol or diethylene glycol could be substituted for the mixed-polyesters. Likewise, any of the monomers from Table I couldbe substituted for the monomers listed in the examples. Also, any of the ammonium salts from Table H could be substituted for the trimethyl amine. hydrochloride or the other ammonium salts listed in the ex-.- amples.

It is to be appreciated that in order to effect a rapid cure of the mixture of polyester and the olefinically unsaturated monomer, a catalyst of the addition reaction involved in copolymerization is usually desirable. stances, e. g. where high curing temperatures or long curing times, orultra-violet irradiation'are available, catalysts may be omitted. V

7 Appropriate catalysts include Benzoyl peroxide Tertiary butyl hydroperoxide Cyclohexyl hydroperoxide Ac tyl per xide Lauroyl peroxide.

' These are merely typical, others are available. The catalysts will usually be employed within a range of .01 to 5%, e. g. 1% ofthemixture. Pref erably the catalyst is added shortly before the mixture is to be polymerized. I

However, in some inperoxide or tertiary hydroperoxide, may be em ployed.

In order to promote the polymerization of a mixture such as above described, a catalyst, e. g. benzoyl peroxide or any of the others in an amount of .1 to 5% is added and the mixture is heated up to an appropriate temperature, for example, to about 93 C. Lower temperatures, say (2., may also be employed. By heating at this latter temperature for a. period of about an hour, the resin can be polymerized to the setting stage. Subsequently, it canbe rendered harder and more durable by balgingat atemperature of about to'200" C, Of course, higher temperatures of baking can b employed, provided they are not so high as to charor discolor the product. The products normally will be clear and strong. The polymerizable mixtures may be cast and cured in suitable molds with or without pressure.

Fillers such as cellulose fibers, asbestos and glass f bers can be added to the polymerizable mixtures in amounts, for example, up to 300% or more. based upon, the polymerizable liquids. Fabrics of glass fibers can also be iimpregnated or coated with the polymerizable mixtures. Mixtures of fibrous material and resin constituents can be heated under pressure to form hard, strong bodies of appropriate form.

Plasticizers such as dimethyl phthalate can also be added to the polymerizable mixtures in amounts, for example, of 5 to 40% based upon polymerizable constituents.

The polymerizable mixtuers can be applied as coatings to metal, wood, paper, cotton or other cloth and cured in situ to for protective films.

A series of compartive tests were preformed designed to show the effects of ammonium salts of aminesas herein described in copolymerizable mixtures of unsaturated polyesters. In these tests, a standard copolymerizable mixture of 1 part by weight of styrene and 2 parts by weight of a mixed polyester of 2.2 mols of 1,2 propylene glycol and a mixture of 1 mol of maleic acid and 1; mol of phthalic acid was employed. The copoly merizable mixture included the several stabilizersor gelation inhibitors to be tested. The stabilized mixtures were subjected to five standardized tests designated respectively as A, B, C, D and E.

.In the first of these. t s s A). a wo Ounce sample of the uncatalyzed copolymerizable mixtune andthe described amount of inhibitor was subjected to. an acceleratedYgelation test in an oven a a c tant te pe a r f F- and t e mix urev was, examined lyv to de e mi e w ele-t e ioc urred- In the second test. (B) about two ounces of the copolymerizable mixture was admixed withv 1.5%

. by weight or benzoyl peroxide as a polymerization Other types of catalysts such as are employed tained the desired stabilizer was admixed with .5% by weight of tertiary butyl hydroperoxide.

The samples for tests B, C and D were stored in a constant temperature room at 77 F. and they were observed frequently for gelation.

In a fifth test (E), the rate of cure of the copolymerizable mixtures was determined by a standardized procedure in which the time requiredfor the samples incuringto reach their socalled peak of their exothermal rise was determined. This procedure was as follows:

An 11 to 12 gram sample of the copolymerizable mixture was admixed with 1.5% of benzoyl peroxide as a polymerization catalyst. The catalyzed mixture was introduced into a test tube 16 millimeters in diameter, to a depth of about 3 inches. A conventional thermocouple which was connected up to a recording Brown Electronik potentiometer, was inserted at the center of the tube to a depth of about one inch above the bottom. The tube was then inserted in a water bath at 180 F. and the recording apparatus was started. The temperature rose to that of the bath, but by reason of the exothermal reaction of polymerization, it ultimately continued to rise to a maximum, termed the Peak Exotherm. The time in minutes required for the mixture to rise from a value of 150 F. to the Peak Exotherm was determined as the rate of cure.

In all tests a standard co-polymerizable mixture of 1 part by weight of styrene and 2 parts by weight of a mixed polyester, which was of 2.2 mols 1,2-propylene glycol, 1 mol maleic acid and 1 mol phthalic acid, was employed.

The data from the several tests are tabulated as follows:

merization have been added. For example, in the case of hydroquinone, it is found that mixtures containing peroxide catalyst and ..l% of the stabilizer will not gel except after several days standing. This mixture would not be satisfactory for many casting operations where cure at a rapid rate and at relatively low temperatures is a requisite.

In the claims, the term ester of ethylenically' unsaturated acid is intended to include mixed esters of the ethylenically unsaturated acid and other acids such as phthalic, succinic, adipicand other. acids which contain no ethylenic unsaturation as well as the unmixed esters thereof.

The examples given herein are to be regarded merely as illustrating the principles of the invention. It will be apparent to those skilledin the art that numerous modifications may be made therein without departure from the spirit of the invention or the scope of the appended claims.

This application is a continuation in. part of my prior applicationsv Serial No. 598,639, filed June 9, 1945, Serial No. 630,551, filed November 23, 1945, andSerial No. 5,684, filed January 31, 1948, each now abandoned.

I claim:

1. A copolymerizable mixture comprising (A) Test A Test B Test 0 Test D Test E 1% 5% No Benzoyl t-butyl t-butyl gjgfgg The Inhibitor Compound catalyst peroxide, hydrohydroa 150 F., Time in peroxide, peroxide, 1 80 Time in hours, 77 F., 77 F., in

days 77 F. Time in Time in minute; V I

hours hours 1% Dicthyl amine hydro chloride 7 l7 2% 3. 2 1% Tributyl amine hydrochloride 7 17 3 3.0 1% Alpha naplithyl amine hydrochloride 4 l7 1% 2.4 .l Triamyl amine hydrochloride 4 l7 2% 2. 4 5.% Trimethyl benzyl ammonium hydroxide 1.5 .1% Hydroquinonc 8 192 216 192 29. 3 1% 4-tertiary butyl catcchol. 8 192 216 72 26. 7 .l% Gatechol 8 192 216 72 7.0 .l% Ascorbic Acid" 0) .l% Alpha naphthoi 5 60 34 1% Tertiary butyl catechol+.00l%

n-butyl amine 9 216 72 1% Sulfur 6 60 34 .l Bcmnlde%yd1e1 E. 1 H. 3 60 34 .l Di nap t -p eny ene iar i iinc f i 6 48-120 216 34 17.4

1 Gelled at once.

It will be appreciated that the copolymerizable mixture employed in the tests without the addition of inhibitor would gel almost immediately upon the combination of the polyester and the styrene or ii gelation did not occur at once, such mixture would gel very quickly when heated to 150 F.

In the table, it will be observed that the mixtures which have been stabilized with hydrochlorides of amines, e. g. diethyl amine hydrochloride, are eiiectively stabilized even at relatively elevated temperatures. The stabilizers have but little effect upon the rate of cure of the copolymerizable mixtures after the catalysts of addition have been incorporated. It will be observed that the stabilized mixtures reach 'a peak exotherm when heated to a temperature of 150 F. within 3 or 4 minutes.

In contradistinction, those compositions containing conventional stabilizers such as hydroquinone or mixtures of tertiary butyl catechol and n-butyl amine are either incompletely stabilized under storage conditions or else they produce an excessive delay in the curing of the copolymerizable mixtures after the catalysts of copolyan ethylenically unsaturated monomer, (B) a polyester of a dihydric alcohol and an alpha beta clicarboxylic, ethylenically unsaturated acid and (C) a small gelation inhibiting amount of a monoamine hydrohalide, said hydrohalide being soluble in the mixture. v

2. A copolymerizable mixture comprising (A) an ethylenically unsaturated monomer, (B) a polyester of a dihydric alcohol and an alpha beta dicarboxylic, alpha ethenically unsaturated acid and (C) a small gelation inhibiting amount of a hydrohalide of a tertiary mcnoamine, said hydrohalide being soluble in the mixture.

3. As a new composition of matter a copolymerizable mixture of styrene and a polyester of a propylene glycol and inaleic acid, said mixture containing in solution a small added inhibiting amount of a gelatin inhibitor which is a salt of a class consisting of trimethyl amine hydrohalide, triethyl amine hydrohalide, dimethyl anilone hydrohalide and pyridyl maleate.

4. A polymerizable mixture comprising a polyester of a glycol and an up ethylenically unsaturated, afi dicarboxylic acid, said mixture further containing in solution therein a small added i 7 gelation inhibiting amount of hydrochloride.

5. The step as defined in claim 19 in which the salt is a halide of a tertiary amine. V

6. The step as defined in claim 19 in which the salt is halide of a tertiary amine containing at least two alkyl groups.

7. The step as defined inclaim- 19 in which. the salt is the halide of a trialkyl amine.

8. The step as defined in claim 19 in which the salt is the halide of a dialkyl aniline. I

9. A polymerizable mixture comprising (A) a polymerizable polyester of a'dihydric alcohol and a dicarboxylic'ethenically unsaturated acid and (B) a small gelation inhibiting amount of a salt of a monoamine and an acid which isno stronger as an oxidizing agent than sulfuric acid and at least as strong in acid value as acetic acid, said salt being non-alkaline andsoluble in the polyester. Y

10. A polymerizable mixture dimethyl aniline comprising (A) a polymerizable polyester of a dihydric alcohol and sulfuric acid and which is at least as strong in acid value as acetic acid, said salt being soluble in'the polyester.

11. A copolymerizable mixture comprising (A) a polymerizable polyester of a dihydric alcohol and an up dicarboxylic ethenically unsaturated (B) an ethylenically unsaturated compound 00- polymerizable with the polyester and (C) a small gelation inhibiting amount of a salt of a monoamine, and an acid which is no stronger as an oxidizing agent than sulfuric acid and which is at least as stron in acid value as acetic acid, said salt being soluble in the mixture.

' 12. A copolymerizable mixture comprising (A) a polymerizable polyester of a glycol and an 11/3 ethylenically unsaturated dicarboxylic acid and (B) a polymerizable compound containing the group C:CH2 and being copolymerizable with the unsaturated polyester and (C) a small gelation inhibiting amount of a salt of a tertiary mono-amine and an acid which is no stronger as an oxidizing'agent than sulfuric acid and which is at least as strong as acid value is acetic acid, said salt being soluble in the mixture.

13. A polymerizable mixture comprisinglA) a polymerizable polyester of a dihydric alcohol and an afi dicarboxylic ethylenically unsaturated acid,

(B) an ethylenically unsaturated compound containing the group C=CH2 and being soluble in and copolymerizable with said polyester and I drohalide salt of a tertiarymonoamine, said salt being soluble in the polyester.

15. In a method of stabilizing a polyester of glycol and an esterifiable acid of a class consisting of an: afl ethylenically unsaturated dicarboxylic acid and a mixture of said acid and a dicarboxylic acid'which'is 'free of ethylenic unsaturation, the steps of dissolving in the mix ture a small, gelation inhibiting amount of a non-alkaline salt of an amine and an acid which is no stronger, as an oxidizing agent than sulfuricacid and atleast as strong in acid valueas acetic acid, said salt being soluble in the mixture and being added tothe polyester while the latter is heated to a temperature adequate to effect ready solution, but below that of decomposition of the salt, and then cooling the mixture to storage temperature.

'16. A polymerizable mixture comprising (A) styrene (B) a polymerizable polyester of a dihydric alcohol and maleic acid and (C) a small gelation inhibiting amount of a tertiary hydrocarbon amine hydrochloric whichis soluble in the mixture.

17. A polymerizable mixture of (A) a polyester of a dihydric alcohol consisting of carbon hydro-' gen and oxygen and an ac ethylenically unsat-' urated afi dicarboxylic acid and (B)fan alphabeta ethylenically unsaturated aralkene compound soluble in and copolymerizable with the polyester and containing a, C=CH2 group, said mixture further containing in solution (C) a small gelation-inhibiting amount of a non-alkaline halide salt of a monoamine in which one to three of the hydrogen atoms of the nitrogen are replaced by saturated hydrocarbon groups.

18. -In a method of preparing a copolymerizable mixture of (A) a polyester of a dihydric alcohol consisting of carbon, hydrogen and oxygen and an alpha-beta ethylenically unsaturated alpha-beta dicarboxylic acid and (B) an ethylenically unsaturated compound containing the group C:CH2 and being soluble in and copolymerizable With said polyester, the step of dissolving in the polyester prior to the addition of the monomer, a small gelation-inhibiting amount of a non-alkaline hydrohalide salt of a tertiary monoamine, said salt being soluble in the poly- I ester, and subsequently adding to the polyester hydrogen and oxygen and an alpha-beta ethylenically unsaturated, alpha-beta dicarboxylic acid and (B) an alpha-beta ethylenically unsaturated aralkene compound soluble in, and copolymerizable with, the polyester and containing a C=CHz group, the step of dissolving in the mixture a small gelation-inhibiting amount of a non-alkaline hydrohalide salt or" a monoamine in which 1 to 3 of the hydrogen atoms attached to the nitrogen are replaced by saturated hydrocarbon groups.

EARL E. PARKER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,225,471 Foord Dec. 17, 1940 2,299,128 vCodd Oct. 20, 1942 2,407,861 Wolk Sept. 17, 1946' 2,409,633 Kropa Oct. 22, 1946 2,452,669 Levine Nov. 2, 1948 2,480,928 Hurdis Sept. 6, 1949 FOREIGN PATENTS Number Country Date Great Britain Oct. 8, 1941 

9. A POLYMERIZABLE MIXTURE COMPRISING (A) A POLYMERIZABLE POLYESTER OF A DIHYDRIC ALCOHOL AND A DICARBOXYLIC ETHENICALLY UNSATURATED ACID AND (B) A SMALL GELATIN INHIBITING AMOUNT OF A SALT OF A MONOAMINE AND AN ACID WHICH IS NO STRONGER AS AN OXIDIZING AGENT THAN SULFURIC ACID AND AT LEAST AS STONG IN ACID VALUE AS ACETIC ACID, SAID SALT BEING NON-ALKALINE AND SOLUBLE IN THE POLYESTER. 